Given:
The given triangle has three equal sides. Thus, the given triangle is an equilateral triangle.
The measure of one angle is (4x - 20)°
Since, it is an equilateral triangle, then all the three sides will be equal.
We need to determine the value of x.
Value of x:
The value of x can be determined using the triangle sum property.
Thus, we have;
[tex](4x-20)^{\circ}+(4x-20)^{\circ}+(4x-20)^{\circ}=180^{\circ}[/tex]
Simplifying, we have;
[tex]4x-20+4x-20+4x-20=180[/tex]
Adding the like terms, we have;
[tex]12x-60=180[/tex]
[tex]12x=240[/tex]
[tex]x=20[/tex]
Thus, the value of x is 20
